JP2011232175A - Method for inspecting wire connection of air/fuel ratio sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inspecting a wire connection of an air/fuel (A/F) ratio sensor in which cracking of a sensor element does not occur.SOLUTION: The present invention provides a method for inspecting a wire connection of an A/F sensor 30 in a vehicle production factory. An electronic control unit (ECU) 15 has a self-diagnosis function to determine that a wire connection of the A/F sensor 30 is normal if a current having a value E higher than a reference current value E1 flows when a predetermined dry condition is met to turn on the A/F sensor 30 for a first predetermined time t1. An inspection controller 25 is connected to the ECU 15 so that a diesel engine 11 is brought into a state in which it has not yet been operated. The inspection controller 25 then causes the ECU 15 to neglect the dry condition so as to forcibly turn on the A/F sensor 30 for a second predetermined time t2. If a current having the value E higher than the reference current value E1 flows, then the wire connection of the A/F sensor 30 is determined to be normal.

Description

  The present invention relates to an air-fuel ratio sensor connection inspection method in a vehicle production factory, and more particularly to an air-fuel ratio sensor connection inspection method provided in an exhaust pipe of a diesel engine.

  Conventionally, air-fuel ratio sensors are known. Patent Document 1 discloses a gas sensor as an air-fuel ratio sensor. For example, in the case of a diesel engine, an air-fuel ratio sensor is provided upstream of the DPF in the exhaust pipe in order to regenerate and control a DPF (Diesel Particulate Filter).

  The air-fuel ratio sensor includes a sensor element and a heater for activating the sensor element. When the air-fuel ratio sensor is energized, the heater heats the surroundings of the sensor element and activates the sensor element. Note that the sensor element of the air-fuel ratio sensor has a problem that the sensor element cracks when it is exposed to water at a high temperature.

  On the other hand, moisture generated by combustion is contained in the exhaust of the diesel engine. For this reason, when the air-fuel ratio sensor provided in the exhaust pipe of the diesel engine is energized, the exhaust pipe needs to be sufficiently dry. Normally, when the air-fuel ratio sensor is energized, that is, when the air-fuel ratio of the exhaust pipe is measured by the air-fuel ratio sensor, and when the air-fuel ratio sensor performs the self-diagnosis control for confirming the connection as will be described later, Only done when the interior is completely dry. The case where the inside of the exhaust pipe is completely dry means that the exhaust temperature, the engine coolant temperature, the catalyst temperature of the DPF, and the like become equal to or higher than a predetermined temperature by operating the engine for a predetermined time as a drying condition. It is a condition.

  In addition, the air-fuel ratio sensor is subjected to self-diagnosis control for confirming the connection as with other sensors. The connection check means checking whether the sensor connector is securely attached or whether the sensor lead is broken. In self-diagnosis control for connection confirmation, an ECU (Engine Control Unit) energizes the air-fuel ratio sensor with electric power supplied from the battery, and when a current value equal to or greater than a predetermined current value flows through the air-fuel ratio sensor, the air-fuel ratio Check that the sensor connection is normal.

  The connection confirmation of the air-fuel ratio sensor is also carried out at the vehicle production factory. However, if the engine has been started in the previous process of the vehicle inspection process, there is a possibility that moisture exists in the exhaust pipe, and if the air-fuel ratio sensor is energized, the sensor element of the air-fuel ratio sensor will be cracked. May occur. Further, in the connection check of the vehicle inspection process, since the vehicle inspection process takes a long time to operate the engine until the dry condition is established so that the self-diagnosis control of the normal connection check is performed, the vehicle inspection process The inspection efficiency is reduced.

JP 2009-150853 A

  The problem to be solved is to provide a connection inspection method for an air-fuel ratio sensor that does not cause sensor element cracking.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, according to the first aspect of the present invention, there is provided a method for inspecting an air-fuel ratio sensor connection in a vehicle production factory, wherein the vehicle production factory includes inspection control means, and the air-fuel ratio sensor is provided in an exhaust pipe of a diesel engine provided in the vehicle. And is connected to a vehicle control means provided in the vehicle. The vehicle control means energizes the air-fuel ratio sensor for a first predetermined period in a state where a predetermined drying condition is satisfied, and A function for self-diagnosis that the connection of the air-fuel ratio sensor is normal when the flowing current value is measured and a current value larger than a reference current value flows during the first predetermined period; Connected to the vehicle control means, the diesel engine is not started yet, and the drying control is confirmed by the inspection control means using the vehicle control means. Without forcibly energizing the air-fuel ratio sensor for a second predetermined period and measuring the current value flowing through the air-fuel ratio sensor, and when a current value greater than a reference current value flows during the second predetermined period Determines that the connection of the air-fuel ratio sensor is normal.

  According to a second aspect of the present invention, in the connection inspection method for an air-fuel ratio sensor according to the first aspect, the second predetermined time period is shorter than the first predetermined period.

  According to the air-fuel ratio sensor connection inspection method of the present invention, sensor element cracks do not occur.

The block diagram which showed the whole structure of the vehicle which concerns on one Embodiment of this invention, and vehicle inspection equipment. The flowchart which shows the flow of the self-diagnosis control of connection confirmation similarly. The flowchart which shows the flow of the connection inspection method of this invention. (A) Time chart of a connection inspection method when the connection inspection is normal, (B) Time chart of the connection inspection method when the connection inspection is abnormal.

  The connection inspection method of the present embodiment is a method for inspecting whether the connection of the A / F sensor 30 provided in the vehicle 10 to be inspected is normal in the vehicle inspection facility 20 that is an inspection facility.

The vehicle 10 and the vehicle inspection facility 20 will be described with reference to FIG.
The vehicle 10 includes a diesel engine 11, an exhaust pipe 12, a DPF (Diesel Particulate Filter) 13, an ECU (Engine Control Unit) 15 as vehicle control means, and an A / F sensor 30 as an air-fuel ratio sensor. It has.

  The exhaust pipe 12 extends from an exhaust manifold (not shown) of the diesel engine 11 to the outside of the vehicle 10. The DPF 13 is a filter that is disposed in the exhaust pipe 12 and collects PM (Particulate Matter) contained in the exhaust gas of the diesel engine 11.

  The ECU 15 is a controller for comprehensively performing electrical control in engine operation by the diesel engine 11 of the vehicle 10, and as a control mode, a normal mode that is a control type in the case of performing normal traveling, and vehicle inspection are performed. And an inspection mode which is a control form when it is made. Further, the ECU 15 has a function of recording a failure code (for example, a failure code C1 described later) and setting a set value (for example, a reference current value E1 described later) in advance.

The A / F sensor 30 will be described.
The A / F sensor 30 is a sensor that detects exhaust gas concentration (oxygen concentration in exhaust gas) when power supplied from a battery (not shown) is energized. The A / F sensor 30 is provided on the upstream side of the DPF 13 in the exhaust pipe 12. The A / F sensor 30 is activated, for example, by raising the temperature to 500 ° C., and the sensor element can detect the exhaust gas concentration (oxygen concentration in the exhaust gas) with high accuracy in the active state. Therefore, the A / F sensor 30 includes an electric heater, which activates the sensor element by the heat generated by the electric heater when energized and maintains the active state of the sensor element.
In addition, the A / F sensor 30 has a problem that the sensor element breaks due to being covered with water in a high temperature state.

  On the other hand, moisture generated by combustion is contained in the exhaust of the diesel engine 11. Therefore, when the A / F sensor 30 provided inside the exhaust pipe 12 of the diesel engine 11 is energized, the inside of the exhaust pipe 12 needs to be sufficiently dry. Therefore, normally, the A / F sensor 30 is energized, that is, when the oxygen concentration of the exhaust gas is measured by the A / F sensor 30, and as will be described later, the A / F sensor 30 performs self-diagnosis control for connection confirmation. Is performed only when the inside of the exhaust pipe 12 is completely dry.

  When the inside of the exhaust pipe 12 is completely dry, the diesel engine 11 is operated for a predetermined time as a drying condition, so that at least the exhaust temperature, the engine coolant temperature, the catalyst temperature of the DPF, etc. are equal to or higher than the predetermined temperature. It is necessary to become. The drying conditions are set in the ECU 15 in advance. In this embodiment, description of the details of the drying conditions is omitted.

The vehicle inspection facility 20 will be described.
The production line of the vehicle factory includes a vehicle assembly line and a vehicle inspection line. The vehicle inspection line includes a vehicle inspection facility 20. In the vehicle inspection facility 20, a connection confirmation inspection of the A / F sensor 30 of the vehicle 10 is performed. The connection confirmation refers to confirming whether the connector of the A / F sensor 30 is securely attached or whether the lead wire connected to the A / F sensor 30 is disconnected.

  The vehicle inspection facility 20 includes an inspection controller 25 as an inspection control means, a table 21, and a communication line 22. The inspection controller 25 is placed on the table 21. When the inspection for confirming the connection of the A / F sensor 30 in the vehicle 10 is performed, the inspection controller 25 is connected to the ECU 15 by the communication line 22.

The flow of self-diagnosis control will be described with reference to FIG.
The ECU 15 has a function of self-diagnosis of the connection confirmation of the A / F sensor 30 (hereinafter, self-diagnosis control). The self-diagnosis control of the connection confirmation means checking whether the connector of the A / F sensor 30 is securely attached or whether the conductor of the A / F sensor 30 is disconnected. The self-diagnosis control for connection confirmation is performed in the normal mode of the ECU 15 and is performed even when the vehicle 10 is traveling.

  In step S110, the ECU 15 confirms whether or not the inside of the exhaust pipe 12 is dried according to the drying conditions. If the drying conditions are satisfied (when all the drying conditions are satisfied), the ECU 15 proceeds to step S120 and performs drying. If the condition is not satisfied, the self-diagnosis control is not performed. In addition, in this embodiment, description is abbreviate | omitted about the detail of drying conditions.

  In step S120, the ECU 15 energizes the A / F sensor 30 with electric power supplied from the battery for a first predetermined time t1. In step S130, the ECU 15 reads (measures) the current value E flowing through the A / F sensor 30 at the first predetermined time t1.

  In step S140, the ECU 15 determines whether or not the read current value E is larger than a preset reference current value E1. If the current value E is larger than the reference current value E1, the ECU 15 ends the self-diagnosis control assuming that the connection is normal. If it is equal to or less than the reference current value E1, it is determined that the connection is abnormal, and the process proceeds to step S150. In step S150, the ECU 15 records the failure code C1 as 1 because the connection of the A / F sensor 30 is abnormal.

  The failure code C <b> 1 is a failure code related to the connection of the A / F sensor 30. That is, if the fault code C1 is 0, the A / F sensor 30 is normally connected. If the fault code C1 is 1, the connection is abnormal, that is, the connector of the A / F sensor 30 is not securely attached, or the conductor of the A / F sensor 30 is disconnected. .

The flow of the connection inspection method of this embodiment will be described with reference to FIG.
When performing the connection inspection of the present embodiment, it is assumed that the inspection controller 25 of the vehicle inspection facility 20 and the ECU 15 of the vehicle 10 are connected by the communication line 22. Further, when the connection inspection of the present embodiment is performed, the vehicle 10 has not yet started the diesel engine 11 in the production line of the vehicle factory, and the ECU 15 is operated by turning on the ignition key. To do.

  In step S210, the inspection controller 25 determines whether the diesel engine 11 is ONF and the ignition key is ON. At this time, “the diesel engine 11 is ONF and the ignition key is ON” means that the diesel engine 11 has not yet been started on the production line of the vehicle factory including the vehicle assembly line and the vehicle inspection line. First, it means that the ECU 15 is operating when the ignition key is turned ON.

  In step S210, the inspection controller 25 proceeds to step S220 if the diesel engine 11 is ONF and the ignition key is ON, and if the diesel engine 11 is ON or the ignition key is ONF. It is assumed that the connection inspection of the A / F sensor 30 is not performed.

  In step S220, the inspection controller 25 switches the control mode of the ECU 15 from the normal mode to the inspection mode. In the inspection mode, the ECU 15 confirms whether or not the drying condition is satisfied because it is clear that the diesel engine 11 has not yet been started for the self-diagnosis control for confirming the connection of the A / F sensor 30 in the normal mode. Without performing this, the self-diagnosis control is performed with the first predetermined time t1 as the second predetermined time t2.

  In the vehicle inspection line, the ECU 15 and the electric circuit such as the battery are more stable than when traveling. Therefore, the inspection time is from the first predetermined time t1, which is the energization time to the A / F sensor 30 of the self-diagnosis control of the ECU 15. The second predetermined time t2 is set to a time shorter than the first predetermined time t1, since the inspection can be carried out with the second predetermined time t2.

  Specifically, the inspection controller 25 causes the ECU 15 to perform self-diagnosis control for confirming the connection of the A / F sensor 30 in steps S230 to S260 (steps surrounded by broken lines in FIG. 3).

  In step S230, the ECU 15 energizes the A / F sensor 30 with electric power supplied from the battery for a second predetermined time t2. In step S240, the ECU 15 reads the current value E flowing through the A / F sensor 30 at the second predetermined time t2.

  In step S250, the ECU 15 determines whether or not the read current value E is larger than a reference current value E1 set in the ECU 15 in advance. If the current value E is larger than the reference current value E1, the ECU 15 determines that the connection is normal and performs self-diagnosis control. If the reference current value E1 or less, the connection is abnormal and the process proceeds to step S260. In step S260, the ECU 15 records the failure code C1 as 1 because the connection is abnormal.

  In step S310, the inspection controller 25 reads the failure code C1 recorded in the ECU 15. In step S320, the inspection controller 25 confirms the failure code C1 recorded in the ECU 15. If the failure code C1 is 0, the inspection controller 25 proceeds to step S330 to pass the connection inspection, and the failure code C1 is 1. In this case, the process proceeds to step S340, and the connection inspection is rejected.

  In the connection inspection method according to the present embodiment, although the diesel engine 11 is not yet started in the production line of the vehicle factory, there is a process in which the diesel engine 11 needs to be started in the vehicle assembly line. Therefore, the process from step S210 to step S260 of the connection inspection method is performed in the process before the diesel engine 11 of the vehicle assembly line is started (process in which the diesel engine 11 is not yet operated), and the connection inspection is performed. The steps from step S310 to step S340 of the method can also be performed on the vehicle inspection line.

The time series change of the connection inspection method of the present embodiment will be described with reference to FIG.
4 (A) and 4 (B) show time-series changes in the current value E and the sensor temperature T, which is the temperature of the A / F sensor 30, in the connection inspection, and FIG. 4 (A) shows normal connection. FIG. 4B shows the current value E and the sensor temperature T when the connection is abnormal.

  4 (A) and 4 (B) show the ON / OFF of the diesel engine 11 shown on the vertical axis, the ON / OFF of the ignition key, the command flag of the inspection controller 25, the ON / OFF of the inspection mode, A The time-series changes of ON / OFF of the / F sensor 30, the current value E, the sensor temperature T, and the failure code C1 are shown on the horizontal axis. Note that the instruction flag of the inspection controller 25 represents 1 when the inspection controller 25 instructs the ECU 15.

  As shown in FIGS. 4 (A) and 4 (B), the inspection mode of the ECU 15 is set to ON by the inspection controller 25 in a state where the diesel engine 11 is set to ONF and the ignition key is set to ON. Electric power supplied from the battery is energized to the A / F sensor 30 for a second predetermined time t2.

  As shown in FIG. 4A, when the A / F sensor 30 connection is normal, the current value E increases with time at the second predetermined time t2 when the A / F sensor 30 is energized, It becomes a value larger than the reference current value E1. At the same time, the sensor temperature T of the A / F sensor 30 also increases.

  As shown in FIG. 4B, when the connection of the A / F sensor 30 is abnormal, the current value E remains 0 at the second predetermined time t2 when the A / F sensor 30 is energized. The reference current value E1 or less. At the same time, the sensor temperature T of the A / F sensor 30 does not rise.

Thus, according to the connection inspection method of the A / F sensor 30 in the vehicle inspection line of the present embodiment, the A / F sensor 30 is energized without starting the diesel engine 11 yet, so the A / F sensor 30. The sensor element is not cracked.
In addition, since the connection inspection is performed using the self-diagnosis control of the ECU 15, the vehicle inspection facility 20 can have a simple configuration.
Furthermore, since the connection inspection is performed without confirming the drying conditions for the self-diagnosis control of the ECU 15, the vehicle inspection time can be shortened.

  Moreover, according to the connection inspection method of the A / F sensor 30 in the vehicle inspection line of the present embodiment, the A / F sensor 30 is implemented by performing the inspection at the second predetermined time t2 shorter than the first predetermined time t1. Since the time during which the temperature is high can be reduced, the risk of sensor element cracking of the A / F sensor 30 can be reduced.

10 Vehicle 11 Diesel Engine 12 Exhaust Pipe 15 ECU (Engine Control Unit)
20 Vehicle inspection equipment 25 Inspection controller 30 A / F sensor C1 Fault code E Current value E1 Reference current value t1 First predetermined time t2 Second predetermined time

Claims (2)

A connection inspection method for an air-fuel ratio sensor in a vehicle production factory,
The vehicle production factory includes inspection control means,
The air-fuel ratio sensor is provided in an exhaust pipe of a diesel engine provided in the vehicle, and is connected to vehicle control means provided in the vehicle.
The vehicle control means energizes the air-fuel ratio sensor for a first predetermined period while a predetermined drying condition is satisfied, measures a current value flowing through the air-fuel ratio sensor, and outputs a reference current value during the first predetermined period. When a larger current value flows, it has a function of self-diagnosis that the connection of the air-fuel ratio sensor is normal,
Connecting the inspection control means to the vehicle control means;
The diesel engine is not yet started,
The inspection control means forcibly energizes the air-fuel ratio sensor for a second predetermined period without using the vehicle control means to check the drying condition, and measures the current value flowing through the air-fuel ratio sensor. When the current value larger than the reference current value flows during the second predetermined period, it is determined that the connection of the air-fuel ratio sensor is normal.
Connection inspection method for air-fuel ratio sensor. A connection inspection method for an air-fuel ratio sensor according to claim 1,
The second predetermined time period is shorter than the first predetermined period;
Connection inspection method for air-fuel ratio sensor.

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